Apparatus for producing or recording electrical impulses



p 1929 L. T. ROBINSON 1,728,880

APPARATUS FOR PRODUCING GI RECORDING ELECTRICAL IMPULSES Filed June 6, 1927 Invenfor Lewis T; Robinson, 5! His Afforne Patented Sept. 17, 1929 UNITED STATES PATENT OFFICE LEWIS '1. ROBINSON, 01' SCHENEC'IADY, NEW YORK, ASSIGNOR '10 GENERAL ELECTRIC COMPANY, A CORPORATION OF .NEW YORK APPARATUS FOR PRODUCING OR RECORDING ELECTRICAL IHI'ULSEB Application filed. June 8, 1927. Serial No. 198,788.

paratus which is readily operated either to produce a record of sound or to produce electrical impulses dependent on the contour of such a record.

Various devices have been utilized in the past to record and reproduce sound either directly or b the eneration of electromagnetic impulses epen ent on the character of the sound to be transmitted. Some of these devices involve the use of parts that are moved in accordance with the contour of a record, such for example as the groove of a phonographic record. Where the use of moving parts is involved, difliculty is frequently encountered due to sound distortion produced by the tendency of these parts to vibrate at a frequency dependent on their free vibration period. In accordance with my invention, this difliculty is minimized or altogether avoided b the provision of an improved apparatus w erein light movable parts are utilized and movement of these parts is damped in a manner to prevent distortion of the impulses to which they are subjected.

My invention will be better understood from the following description when considered in connection with the accompanying drawingsand its scope will be pointed out in the appended claims.

Referring to the drawings, Figs. 1 and 2 show diflere'nt views of an apparatus wherein my invention has been embodied.

This ap aratus comprises a pair of mag netic mem ers 1 and 2 arranged to form an air ap between their ole pieces. These mem ers are fixed to an msulation support 3 by'means of non-magnetic clamping members 4 and 5 between which a resilient member or spring 6 is supported. At a point intermediate its ends the spring 6 is attached to a movable member 7 which may be either a record cutter or a phonographic needle adapted to cooperate with a record disk 8.

A conductor 9, located in the air gap between the magnetic members 1 and 2 and connected between a pair of terminals 10 and 11,

is attached to the member 7 and is arranged to be subjected to a tension which is dependent on the adjustment of nuts 12 to 15. It will be observed that the nuts 14 and 15 are threaded on bolts 16 and 17 respectively, and that these bolts are mechanically connected to the conductor 9 through resilient members shown as springs 18 and 19 and are suspended from members 20 and 21 each attached to the insulation support 3. The part of the apparatus located above the support 3 is enclosed in a cover 22 which contains a damping fluid such as oil or the like.

Assuming the needle or cutter 7 to be out of engagement with the disk 8 and no current to'be transmitted through the conductor 9, the position of the member 7 is dependent on the resultant tension of the springs 6, 18 and 19 and may be that illustrated in the drawings. When current is transmitted through the conductor 9, however, the two halves of the conductor 9 are subjected to forces which tend to move the member 7 to the right or to the left depending on the direction of the current in the conductor 9. When the member 7 is moved to and fro in accordance with the contour of the groove in a record, the conductor 9 cuts the flux of the air gap and an electromotive force dependent on the contour of this groove is produced in the conductor 9. The use of the springs 18 and 19 has the advantage that any tendency of the apparatus to operate at double the frequency of the current transmitted through the conductor 9 is eliminated. It will be readily understood that, due to the fact that the member 7 has little mechanical inertia and the movement of the conductor 9 is damped by the springs 18 and 19, there is little, if any, tendency for these parts to vibrate in a man.- ner to distort the impulses to which the apparatus is subjected.

Certain features of this apparatus are broadly claimed in my copending application Ser. No. 174,355, filed March 10, 1927, and assigned to the same assignee as the present application.

The embodiments of the invention illustrated and described herein have been selected for the purpose of clearly setting forth the Erinciples involved. It will be apparent, owever, that the invention is susceptible of being modified to meet the different conditions encountered in its use and I therefore aim to cover by the appended claims all modifications within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. 'The combination of magnetic means arranged to form an air gap, a movable member provided with a resilient support, a con? ductor located in said air gap and attached to said member, and resilient means directly connected to said conductor for subjecting said conductor to a predetermined tensile force.

2. The combination of magnetic means arranged to form an air gap, a movable member provided with a! resilient support, a conductor located in said air gap and attached to said member, and resilient means attached to said conductor on opposite sides of said -m'ember for subjecting said conductor to a tensile force.

3. The combination of magnetic means arranged to form an air gap, a movable member provided with a resilient support, a conductor located in said air gap and attached to said member, resilient means attached to said conductor on opposite sides of said member for subjecting said conductor to a tensile force, and means for adjusting the magnitude of said force.

4. A speech current apparatus including means for producing a magnetic field, a casing, a fluid within said casing, a resilient member, a movable member supported by said resilient member and arranged to extend through said casing, and a conductor mounted in said magnetic field and in said liquid and connected to said movable member.

5. A speech current apparatus including means for producing a magnetic field, a casing, a fluid within said casing, a resilient -member, a movable member supported by said resilient member and arranged to extend through said casing, a conductor mounted in said magnetic field and in said liquid and connected to said movable member, and means attached to said conductor on opposite sides of said movable member for subjecting said conductor to a mechanical force which tends to maintain said movable member in a predetermined position.

In witness whereof, I have hereunto set my hand this 3d day of June, 1927.

LEWIS T. ROBINSON. 

